Churchill Downs scrapped the old "graded stakes earnings" system with one that more resembles a play-off.

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LOUISVILLE, KY - MAY 05: The field comes down the front stretch during the 138th running of the Kentucky Derby at Churchill Downs on May 5, 2012 in Louisville, Kentucky. (Photo by Andy Lyons/Getty Images)

Ask a casual horse racing fan what “graded stakes earnings” are, and you’re likely to get a shrug.

That’s what officials at Churchill Downs, the site of the Kentucky Derby, found when they polled fans around the country last year. More than 80 percent said they had no idea how a horse qualified for the sport’s biggest race.

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The officials were already unhappy with the existing system, which often allowed marginal horses to join the race just because they’d won a lot of cash. Some were gaining berths based on races they’d run many months earlier, or with help from tracks backed by new casino money.

Sometimes the 20-horse field would include as many as a half-dozen entrants who many insiders believed didn’t belong.

“We realized we didn’t have much control over who was getting into our field,” Churchill Downs spokesman Darren Rogers said.

So the track scrapped the graded stakes system and started a new one that resembles a traditional playoff schedule. This year’s Kentucky Derby is the first to operate with that program, which awards points to winners of an increasingly challenging series of races.

Supporters say the system is fairer because it awards horses that distinguish themselves in the weeks leading up to the Derby.

“There are no horses back-dooring it into the race,” said journalist Steve Haskin. “Here, it’s, ‘What have you done for me lately?’”

The new system awards points to 36 races that start in late September and continue until the week before the May 4 Derby. The last few races, considered the most elite and competitive, offer the most points.

That makes it easier and more fun for fans to follow, and requires more strategy of owners and trainers, officials say.

“It will separate the pretenders from the contenders,” said Eric Wing, spokesman for the National Thoroughbred Racing Association.

One of the casualties of the new system was Shanghai Bobby. He has more than $1.7 million in earnings, the most of any in the field, most of it earned last year. Under the graded stakes system, he would have been guaranteed a spot in the Derby. But a fifth place finish in the Florida Derby on March 30 forced his owners to pull him from contention.

“If the old system was in place, he would have had the starting gate waiting for him in Louisville,” Wing said. “Whereas this year, he’s out in the cold.”

As of late April, there were more than 20 horses on the leaderboard with enough points for a shot at the Derby. Some of those horses may be pulled by their trainers for various concern. Tie-breaking rules could turn on earnings.

That left several horses on the bubble, with just a few days before the race.

And that’s the point: making sure that only the best horses run.

“We think this has the chance to be the most competitive top-to-bottom field in quite some time,” Rogers said.